Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

 131

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

Multiply, Multiply with Accumulate, and Multiply with Subtract, using 32-bit operands, and producing a 32-bit result.

Syntax

MUL{S}{cond} {Rd,} Rn, Rm ; Multiply

MLA{cond} Rd, Rn, Rm, Ra  ; Multiply with accumulate

MLS{cond} Rd, Rn, Rm, Ra  ; Multiply with subtract

where:

cond

S

is an optional suffix. If S is specified, the condition code flags are updated on the result  of  the  operation,

see 

.

Rd

is the destination register. If Rd is omitted, the destination register is Rn.

Rn, Rm

are registers holding the values to be multiplied.

Ra

is a register holding the value to be added or subtracted from.

Operation

The MUL instruction multiplies the values from Rn and Rm, and places the least significant 32 bits of the result in Rd.

The MLA instruction multiplies the values from Rn and Rm, adds the value from Ra, and places the least significant 32
bits of the result in Rd.

The MLS instruction multiplies the values from Rn and Rm, subtracts the product from the value from Ra, and places the
least significant 32 bits of the result in Rd.

The results of these instructions do not depend on whether the operands are signed or unsigned.

Restrictions

In these instructions, do not use SP and do not use PC.

If the S suffix is used with the MUL instruction:



Rd, Rn, and Rm must all be in the range R0 to R7



Rd must be the same as Rm



The cond suffix must not be used.

Condition Flags

If S is specified, the MUL instruction:



Updates the N and Z flags according to the result



Does not affect the C and V flags.

Examples

   MUL    R10, R2, R5     ; Multiply, R10 = R2 x R5

   MLA    R10, R2, R1, R5 ; Multiply with accumulate, R10 = (R2 x R1) + R5

   MULS   R0, R2, R2      ; Multiply with flag update, R0 = R2 x R2

   MULLT  R2, R3, R2      ; Conditionally multiply, R2 = R3 x R2

   MLS    R4, R5, R6, R7  ; Multiply with subtract, R4 = R7 - (R5 x R6)